/**********************************************************************
 *
 * GEOS - Geometry Engine Open Source
 * http://geos.osgeo.org
 *
 * Copyright (C) 2005-2006 Refractions Research Inc.
 * Copyright (C) 2001-2002 Vivid Solutions Inc.
 *
 * This is free software; you can redistribute and/or modify it under
 * the terms of the GNU Lesser General Public Licence as published
 * by the Free Software Foundation.
 * See the COPYING file for more information.
 *
 ***********************************************************************
 *
 * Last port: operation/overlay/OverlayOp.java r567 (JTS-1.12+)
 *
 **********************************************************************/

#include <geos/constants.h>
#include <geos/operation/overlay/OverlayOp.h>
#include <geos/operation/overlay/validate/OverlayResultValidator.h>
#include <geos/operation/overlay/ElevationMatrix.h>
#include <geos/operation/overlay/OverlayNodeFactory.h>
#include <geos/operation/overlay/PolygonBuilder.h>
#include <geos/operation/overlay/LineBuilder.h>
#include <geos/operation/overlay/PointBuilder.h>
#include <geos/geom/Geometry.h>
#include <geos/geom/Coordinate.h>
#include <geos/geom/GeometryFactory.h>
#include <geos/geom/Polygon.h>
#include <geos/geom/LineString.h>
#include <geos/geom/Point.h>
#include <geos/geom/PrecisionModel.h>
#include <geos/geomgraph/Label.h>
#include <geos/geomgraph/Edge.h>
#include <geos/geomgraph/Node.h>
#include <geos/geomgraph/GeometryGraph.h>
#include <geos/geomgraph/EdgeEndStar.h>
#include <geos/geomgraph/DirectedEdgeStar.h>
#include <geos/geomgraph/DirectedEdge.h>
#include <geos/geomgraph/Position.h>
#include <geos/geomgraph/index/SegmentIntersector.h>
#include <geos/util/Interrupt.h>
#include <geos/util/TopologyException.h>
#include <geos/geomgraph/EdgeNodingValidator.h>
#include <geos/util.h>

#include <cassert>
#include <cmath>
#include <vector>
#include <sstream>
#include <memory> // for unique_ptr

#ifndef GEOS_DEBUG
#define GEOS_DEBUG 0
#endif

#define COMPUTE_Z 1
#define USE_ELEVATION_MATRIX 1
#define USE_INPUT_AVGZ 0

// A result validator using FuzzyPointLocator to
// check validity of result. Pretty expensive...
//#define ENABLE_OVERLAY_RESULT_VALIDATOR 1

// Edge noding validator, more lightweighted and
// catches robustness errors earlier
#define ENABLE_EDGE_NODING_VALIDATOR 1

// Define this to get some reports about validations
//#define GEOS_DEBUG_VALIDATION 1

// Other validators, not found in JTS
//#define ENABLE_OTHER_OVERLAY_RESULT_VALIDATORS 1

using namespace std;
using namespace geos::geom;
using namespace geos::geomgraph;
using namespace geos::algorithm;

namespace geos {
namespace operation { // geos.operation
namespace overlay { // geos.operation.overlay

/* static public */
Geometry*
OverlayOp::overlayOp(const Geometry* geom0, const Geometry* geom1,
                     OverlayOp::OpCode opCode)
// throw(TopologyException *)
{
    OverlayOp gov(geom0, geom1);
    return gov.getResultGeometry(opCode);
}

/* static public */
bool
OverlayOp::isResultOfOp(const Label& label, OverlayOp::OpCode opCode)
{
    Location loc0 = label.getLocation(0);
    Location loc1 = label.getLocation(1);
    return isResultOfOp(loc0, loc1, opCode);
}


/* static public */
bool
OverlayOp::isResultOfOp(Location loc0, Location loc1, OverlayOp::OpCode opCode)
{
    if(loc0 == Location::BOUNDARY) {
        loc0 = Location::INTERIOR;
    }
    if(loc1 == Location::BOUNDARY) {
        loc1 = Location::INTERIOR;
    }
    switch(opCode) {
    case opINTERSECTION:
        return loc0 == Location::INTERIOR && loc1 == Location::INTERIOR;
    case opUNION:
        return loc0 == Location::INTERIOR || loc1 == Location::INTERIOR;
    case opDIFFERENCE:
        return loc0 == Location::INTERIOR && loc1 != Location::INTERIOR;
    case opSYMDIFFERENCE:
        return (loc0 == Location::INTERIOR && loc1 != Location::INTERIOR)
               || (loc0 != Location::INTERIOR && loc1 == Location::INTERIOR);
    }
    return false;
}

OverlayOp::OverlayOp(const Geometry* g0, const Geometry* g1)

    :

    // this builds graphs in arg[0] and arg[1]
    GeometryGraphOperation(g0, g1),

    /*
     * Use factory of primary geometry.
     * Note that this does NOT handle mixed-precision arguments
     * where the second arg has greater precision than the first.
     */
    geomFact(g0->getFactory()),

    resultGeom(nullptr),
    graph(OverlayNodeFactory::instance()),
    resultPolyList(nullptr),
    resultLineList(nullptr),
    resultPointList(nullptr)

{

#if COMPUTE_Z
#if USE_INPUT_AVGZ
    avgz[0] = DoubleNotANumber;
    avgz[1] = DoubleNotANumber;
    avgzcomputed[0] = false;
    avgzcomputed[1] = false;
#endif // USE_INPUT_AVGZ

    Envelope env(*(g0->getEnvelopeInternal()));
    env.expandToInclude(g1->getEnvelopeInternal());
#if USE_ELEVATION_MATRIX
    elevationMatrix = new ElevationMatrix(env, 3, 3);
    elevationMatrix->add(g0);
    elevationMatrix->add(g1);
#if GEOS_DEBUG
    cerr << elevationMatrix->print() << endl;
#endif
#endif // USE_ELEVATION_MATRIX
#endif // COMPUTE_Z
}

OverlayOp::~OverlayOp()
{
    delete resultPolyList;
    delete resultLineList;
    delete resultPointList;
    for(size_t i = 0; i < dupEdges.size(); i++) {
        delete dupEdges[i];
    }
#if USE_ELEVATION_MATRIX
    delete elevationMatrix;
#endif
}

/*public*/
Geometry*
OverlayOp::getResultGeometry(OverlayOp::OpCode funcCode)
//throw(TopologyException *)
{
    computeOverlay(funcCode);
    return resultGeom;
}

/*private*/
void
OverlayOp::insertUniqueEdges(vector<Edge*>* edges, const Envelope* env)
{
    for(size_t i = 0, n = edges->size(); i < n; ++i) {
        Edge* e = (*edges)[i];
        if(env && ! env->intersects(e->getEnvelope())) {
            dupEdges.push_back(e); // or could it be deleted directly ?
            continue;
        }
#if GEOS_DEBUG
        cerr << " " << e->print() << endl;
#endif
        insertUniqueEdge(e);
    }
}

/*private*/
void
OverlayOp::replaceCollapsedEdges()
{
    vector<Edge*>& edges = edgeList.getEdges();

    for(size_t i = 0, nedges = edges.size(); i < nedges; ++i) {
        Edge* e = edges[i];
        assert(e);
        if(e->isCollapsed()) {
#if GEOS_DEBUG
            cerr << " replacing collapsed edge " << i << endl;
#endif // GEOS_DEBUG
            //Debug.print(e);
            edges[i] = e->getCollapsedEdge();

            // should we keep this alive some more ?
            delete e;
        }
    }
}

/*private*/
void
OverlayOp::copyPoints(int argIndex, const Envelope* env)
{
//#define GEOS_DEBUG_COPY_POINTS 1

#ifdef GEOS_DEBUG_COPY_POINTS
    int copied = 0;
#endif

    //env = 0; // WARNING: uncomment to disable env-optimization

    // TODO: set env to null if it covers arg geometry envelope

    NodeMap::container& nodeMap = arg[argIndex]->getNodeMap()->nodeMap;
    for(NodeMap::const_iterator it = nodeMap.begin(), itEnd = nodeMap.end();
            it != itEnd; ++it) {
        Node* graphNode = it->second;
        assert(graphNode);
        const Coordinate& coord = graphNode->getCoordinate();

        if(env && ! env->covers(coord)) {
            continue;
        }

#ifdef GEOS_DEBUG_COPY_POINTS
        ++copied;
#endif
        Node* newNode = graph.addNode(coord);
        assert(newNode);

        newNode->setLabel(argIndex, graphNode->getLabel().getLocation(argIndex));
    }

#ifdef GEOS_DEBUG_COPY_POINTS
    cerr << "Copied " << copied << " nodes out of " << nodeMap.size() << " for geom " << argIndex << endl;
#endif
}

/*private*/
void
OverlayOp::computeLabelling()
//throw(TopologyException *) // and what else ?
{
    NodeMap::container& nodeMap = graph.getNodeMap()->nodeMap;

#if GEOS_DEBUG
    cerr << "OverlayOp::computeLabelling(): at call time: " << edgeList.print() << endl;
#endif

#if GEOS_DEBUG
    cerr << "OverlayOp::computeLabelling() scanning " << nodeMap.size() << " nodes from map:" << endl;
#endif

    for(NodeMap::const_iterator it = nodeMap.begin(), itEnd = nodeMap.end();
            it != itEnd; ++it) {
        Node* node = it->second;
#if GEOS_DEBUG
        cerr << "     " << node->print() << " has " << node->getEdges()->getEdges().size() << " edgeEnds" << endl;
#endif
        node->getEdges()->computeLabelling(&arg);
    }
#if GEOS_DEBUG
    cerr << "OverlayOp::computeLabelling(): after edge labelling: " << edgeList.print() << endl;
#endif
    mergeSymLabels();
#if GEOS_DEBUG
    cerr << "OverlayOp::computeLabelling(): after labels sym merging: " << edgeList.print() << endl;
#endif
    updateNodeLabelling();
#if GEOS_DEBUG
    cerr << "OverlayOp::computeLabelling(): after node labeling update: " << edgeList.print() << endl;
#endif
}

/*private*/
void
OverlayOp::mergeSymLabels()
{
    NodeMap::container& nodeMap = graph.getNodeMap()->nodeMap;

#if GEOS_DEBUG
    cerr << "OverlayOp::mergeSymLabels() scanning " << nodeMap.size() << " nodes from map:" << endl;
#endif

    for(NodeMap::const_iterator it = nodeMap.begin(), itEnd = nodeMap.end();
            it != itEnd; ++it) {
        Node* node = it->second;
        EdgeEndStar* ees = node->getEdges();
        detail::down_cast<DirectedEdgeStar*>(ees)->mergeSymLabels();
        //((DirectedEdgeStar*)node->getEdges())->mergeSymLabels();
#if GEOS_DEBUG
        cerr << "     " << node->print() << endl;
#endif
        //node.print(System.out);
    }
}

/*private*/
void
OverlayOp::updateNodeLabelling()
{
    // update the labels for nodes
    // The label for a node is updated from the edges incident on it
    // (Note that a node may have already been labelled
    // because it is a point in one of the input geometries)

    NodeMap::container& nodeMap = graph.getNodeMap()->nodeMap;

#if GEOS_DEBUG
    cerr << "OverlayOp::updateNodeLabelling() scanning "
         << nodeMap.size() << " nodes from map:" << endl;
#endif

    for(NodeMap::const_iterator it = nodeMap.begin(), itEnd = nodeMap.end();
            it != itEnd; ++it) {
        Node* node = it->second;
        EdgeEndStar* ees = node->getEdges();
        DirectedEdgeStar* des = detail::down_cast<DirectedEdgeStar*>(ees);
        Label& lbl = des->getLabel();
        node->getLabel().merge(lbl);
#if GEOS_DEBUG
        cerr << "     " << node->print() << endl;
#endif
    }
}

/*private*/
void
OverlayOp::labelIncompleteNodes()
{
    NodeMap::container& nodeMap = graph.getNodeMap()->nodeMap;

#if GEOS_DEBUG
    cerr << "OverlayOp::labelIncompleteNodes() scanning " << nodeMap.size() << " nodes from map:" << endl;
#endif

    for(NodeMap::const_iterator it = nodeMap.begin(), itEnd = nodeMap.end();
            it != itEnd; ++it) {
        Node* n = it->second;
        const Label& label = n->getLabel();
        if(n->isIsolated()) {
            if(label.isNull(0)) {
                labelIncompleteNode(n, 0);
            }
            else {
                labelIncompleteNode(n, 1);
            }
        }
        // now update the labelling for the DirectedEdges incident on this node
        EdgeEndStar* ees = n->getEdges();
        DirectedEdgeStar* des = detail::down_cast<DirectedEdgeStar*>(ees);

        des->updateLabelling(label);
        //((DirectedEdgeStar*)n->getEdges())->updateLabelling(label);
        //n.print(System.out);
    }
}

/*private*/
void
OverlayOp::labelIncompleteNode(Node* n, int targetIndex)
{
#if GEOS_DEBUG
    cerr << "OverlayOp::labelIncompleteNode(" << n->print() << ", " << targetIndex << ")" << endl;
#endif
    const Geometry* targetGeom = arg[targetIndex]->getGeometry();
    Location loc = ptLocator.locate(n->getCoordinate(), targetGeom);
    n->getLabel().setLocation(targetIndex, loc);

#if GEOS_DEBUG
    cerr << "   after location set: " << n->print() << endl;
#endif

#if COMPUTE_Z
    /*
     * If this node has been labeled INTERIOR of a line
     * or BOUNDARY of a polygon we must merge
     * Z values of the intersected segment.
     * The intersection point has been already computed
     * by LineIntersector invoked by PointLocator.
     */

    // Only do this if input does have Z
    // See https://trac.osgeo.org/geos/ticket/811
    if(targetGeom->getCoordinateDimension() < 3) {
        return;
    }

    const LineString* line = dynamic_cast<const LineString*>(targetGeom);
    if(loc == Location::INTERIOR && line) {
        mergeZ(n, line);
    }
    const Polygon* poly = dynamic_cast<const Polygon*>(targetGeom);
    if(loc == Location::BOUNDARY && poly) {
        mergeZ(n, poly);
    }
#if USE_INPUT_AVGZ
    if(loc == Location::INTERIOR && poly) {
        n->addZ(getAverageZ(targetIndex));
    }
#endif // USE_INPUT_AVGZ
#endif // COMPUTE_Z
}

/*static private*/
double
OverlayOp::getAverageZ(const Polygon* poly)
{
    double totz = 0.0;
    int zcount = 0;

    const CoordinateSequence* pts =
        poly->getExteriorRing()->getCoordinatesRO();
    size_t npts = pts->getSize();
    for(size_t i = 0; i < npts; ++i) {
        const Coordinate& c = pts->getAt(i);
        if(!std::isnan(c.z)) {
            totz += c.z;
            zcount++;
        }
    }

    if(zcount) {
        return totz / zcount;
    }
    else {
        return DoubleNotANumber;
    }
}

/*private*/
double
OverlayOp::getAverageZ(int targetIndex)
{
    if(avgzcomputed[targetIndex]) {
        return avgz[targetIndex];
    }

    const Geometry* targetGeom = arg[targetIndex]->getGeometry();

    // OverlayOp::getAverageZ(int) called with a ! polygon
    assert(targetGeom->getGeometryTypeId() == GEOS_POLYGON);

    const Polygon* p = dynamic_cast<const Polygon*>(targetGeom);
    avgz[targetIndex] = getAverageZ(p);
    avgzcomputed[targetIndex] = true;
    return avgz[targetIndex];
}

/*private*/
int
OverlayOp::mergeZ(Node* n, const Polygon* poly) const
{
    const LineString* ls;
    int found = 0;
    ls = poly->getExteriorRing();
    found = mergeZ(n, ls);
    if(found) {
        return 1;
    }
    for(size_t i = 0, nr = poly->getNumInteriorRing(); i < nr; ++i) {
        ls = poly->getInteriorRingN(i);
        found = mergeZ(n, ls);
        if(found) {
            return 1;
        }
    }
    return 0;
}

/*private*/
int
OverlayOp::mergeZ(Node* n, const LineString* line) const
{
    const CoordinateSequence* pts = line->getCoordinatesRO();
    const Coordinate& p = n->getCoordinate();
    LineIntersector p_li;
    for(size_t i = 1, size = pts->size(); i < size; ++i) {
        const Coordinate& p0 = pts->getAt(i - 1);
        const Coordinate& p1 = pts->getAt(i);
        p_li.computeIntersection(p, p0, p1);
        if(p_li.hasIntersection()) {
            if(p == p0) {
                n->addZ(p0.z);
            }
            else if(p == p1) {
                n->addZ(p1.z);
            }
            else {
                n->addZ(LineIntersector::interpolateZ(p,
                                                      p0, p1));
            }
            return 1;
        }
    }
    return 0;
}

/*private*/
void
OverlayOp::findResultAreaEdges(OverlayOp::OpCode opCode)
{
    vector<EdgeEnd*>* ee = graph.getEdgeEnds();
    for(size_t i = 0, e = ee->size(); i < e; ++i) {
        DirectedEdge* de = (DirectedEdge*)(*ee)[i];
        // mark all dirEdges with the appropriate label
        const Label& label = de->getLabel();
        if(label.isArea()
                && !de->isInteriorAreaEdge()
                && isResultOfOp(label.getLocation(0, Position::RIGHT),
                                label.getLocation(1, Position::RIGHT),
                                opCode)
          ) {
            de->setInResult(true);
            //Debug.print("in result "); Debug.println(de);
        }
    }
}

/*private*/
void
OverlayOp::cancelDuplicateResultEdges()
{
    // remove any dirEdges whose sym is also included
    // (they "cancel each other out")
    vector<EdgeEnd*>* ee = graph.getEdgeEnds();
    for(size_t i = 0, eesize = ee->size(); i < eesize; ++i) {
        DirectedEdge* de = static_cast<DirectedEdge*>((*ee)[i]);
        DirectedEdge* sym = de->getSym();
        if(de->isInResult() && sym->isInResult()) {
            de->setInResult(false);
            sym->setInResult(false);
            //Debug.print("cancelled "); Debug.println(de); Debug.println(sym);
        }
    }
}

/*public*/
bool
OverlayOp::isCoveredByLA(const Coordinate& coord)
{
    if(isCovered(coord, resultLineList)) {
        return true;
    }
    if(isCovered(coord, resultPolyList)) {
        return true;
    }
    return false;
}

/*public*/
bool
OverlayOp::isCoveredByA(const Coordinate& coord)
{
    if(isCovered(coord, resultPolyList)) {
        return true;
    }
    return false;
}

/*private*/
bool
OverlayOp::isCovered(const Coordinate& coord, vector<Geometry*>* geomList)
{
    for(size_t i = 0, n = geomList->size(); i < n; ++i) {
        Geometry* geom = (*geomList)[i];
        Location loc = ptLocator.locate(coord, geom);
        if(loc != Location::EXTERIOR) {
            return true;
        }
    }
    return false;
}

/*private*/
bool
OverlayOp::isCovered(const Coordinate& coord, vector<LineString*>* geomList)
{
    for(size_t i = 0, n = geomList->size(); i < n; ++i) {
        Geometry* geom = (Geometry*)(*geomList)[i];
        Location loc = ptLocator.locate(coord, geom);
        if(loc != Location::EXTERIOR) {
            return true;
        }
    }
    return false;
}

/*private*/
bool
OverlayOp::isCovered(const Coordinate& coord, vector<Polygon*>* geomList)
{
    for(size_t i = 0, n = geomList->size(); i < n; ++i) {
        Geometry* geom = (Geometry*)(*geomList)[i];
        Location loc = ptLocator.locate(coord, geom);
        if(loc != Location::EXTERIOR) {
            return true;
        }
    }
    return false;
}

Dimension::DimensionType
OverlayOp::resultDimension(OverlayOp::OpCode overlayOpCode,
                           const Geometry* g0, const Geometry* g1)
{
    Dimension::DimensionType dim0 = g0->getDimension();
    Dimension::DimensionType dim1 = g1->getDimension();

    Dimension::DimensionType resultDimension = Dimension::False;
    switch(overlayOpCode) {
    case OverlayOp::opINTERSECTION:
        resultDimension = min(dim0, dim1);
        break;
    case OverlayOp::opUNION:
        resultDimension = max(dim0, dim1);
        break;
    case OverlayOp::opDIFFERENCE:
        resultDimension = dim0;
        break;
    case OverlayOp::opSYMDIFFERENCE:
        resultDimension = max(dim0, dim1);
        break;
    }
    return resultDimension;
}

std::unique_ptr<geom::Geometry>
OverlayOp::createEmptyResult(OverlayOp::OpCode overlayOpCode,
                             const geom::Geometry* a, const geom::Geometry* b,
                             const GeometryFactory* geomFact)
{
    std::unique_ptr<geom::Geometry> result = nullptr;
    switch(resultDimension(overlayOpCode, a, b)) {
    case Dimension::P:
        result = geomFact->createPoint();
        break;
    case Dimension::L:
        result = geomFact->createLineString();
        break;
    case Dimension::A:
        result = geomFact->createPolygon();
        break;
    default:
        result = geomFact->createGeometryCollection();
        break;
    }
    return result;
}

/*private*/
Geometry*
OverlayOp::computeGeometry(vector<Point*>* nResultPointList,
                           vector<LineString*>* nResultLineList,
                           vector<Polygon*>* nResultPolyList,
                           OverlayOp::OpCode opCode)
{
    size_t nPoints = nResultPointList->size();
    size_t nLines = nResultLineList->size();
    size_t nPolys = nResultPolyList->size();

    std::unique_ptr<vector<Geometry*>> geomList{new vector<Geometry*>()};
    geomList->reserve(nPoints + nLines + nPolys);

    // element geometries of the result are always in the order P,L,A
    geomList->insert(geomList->end(),
                     nResultPointList->begin(),
                     nResultPointList->end());

    geomList->insert(geomList->end(),
                     nResultLineList->begin(),
                     nResultLineList->end());

    geomList->insert(geomList->end(),
                     nResultPolyList->begin(),
                     nResultPolyList->end());


    if(geomList->empty()) {
        return createEmptyResult(opCode, arg[0]->getGeometry(),
                                 arg[1]->getGeometry(), geomFact).release();
    }
    // build the most specific geometry possible
    Geometry* g = geomFact->buildGeometry(geomList.release());
    return g;
}

/*private*/
void
OverlayOp::computeOverlay(OverlayOp::OpCode opCode)
//throw(TopologyException *)
{

    // Compute the target envelope
    const Envelope* env = nullptr;
    const Envelope* env0 = getArgGeometry(0)->getEnvelopeInternal();
    const Envelope* env1 = getArgGeometry(1)->getEnvelopeInternal();
    Envelope opEnv;
    if(resultPrecisionModel->isFloating()) {
        // Envelope-based optimization only works in floating precision
        switch(opCode) {
        case opINTERSECTION:
            env0->intersection(*env1, opEnv);
            env = &opEnv;
            break;
        case opDIFFERENCE:
            opEnv = *env0;
            env = &opEnv;
            break;
        default:
            break;
        }
    }
    //env = 0; // WARNING: uncomment to disable env-optimization

    // copy points from input Geometries.
    // This ensures that any Point geometries
    // in the input are considered for inclusion in the result set
    copyPoints(0, env);
    copyPoints(1, env);

    GEOS_CHECK_FOR_INTERRUPTS();

    // node the input Geometries
    arg[0]->computeSelfNodes(li, false, env);
    GEOS_CHECK_FOR_INTERRUPTS();
    arg[1]->computeSelfNodes(li, false, env);

#if GEOS_DEBUG
    cerr << "OverlayOp::computeOverlay: computed SelfNodes" << endl;
#endif

    GEOS_CHECK_FOR_INTERRUPTS();

    // compute intersections between edges of the two input geometries
    arg[0]->computeEdgeIntersections(arg[1], &li, true, env);

#if GEOS_DEBUG
    cerr << "OverlayOp::computeOverlay: computed EdgeIntersections" << endl;
    cerr << "OverlayOp::computeOverlay: li: " << li.toString() << endl;
#endif


    GEOS_CHECK_FOR_INTERRUPTS();

    vector<Edge*> baseSplitEdges;
    arg[0]->computeSplitEdges(&baseSplitEdges);
    GEOS_CHECK_FOR_INTERRUPTS();
    arg[1]->computeSplitEdges(&baseSplitEdges);

    GEOS_CHECK_FOR_INTERRUPTS();

    // add the noded edges to this result graph
    insertUniqueEdges(&baseSplitEdges, env);
    computeLabelsFromDepths();
    replaceCollapsedEdges();
    //Debug.println(edgeList);

    GEOS_CHECK_FOR_INTERRUPTS();

#ifdef ENABLE_EDGE_NODING_VALIDATOR // {
    /*
     * Check that the noding completed correctly.
     *
     * This test is slow, but necessary in order to catch
     * robustness failure situations.
     * If an exception is thrown because of a noding failure,
     * then snapping will be performed, which will hopefully avoid
     * the problem.
     * In the future hopefully a faster check can be developed.
     *
     */
    try {
#ifdef GEOS_DEBUG_VALIDATION
        cout << "EdgeNodingValidator about to evaluate " << edgeList.getEdges().size() << " edges" << endl;
#endif
        // Will throw TopologyException if noding is
        // found to be invalid
        EdgeNodingValidator::checkValid(edgeList.getEdges());
#ifdef GEOS_DEBUG_VALIDATION
        cout << "EdgeNodingValidator accepted the noding" << endl;
#endif
    }
    catch(const util::TopologyException& ex) {
#ifdef GEOS_DEBUG_VALIDATION
        cout << "EdgeNodingValidator found noding invalid: " << ex.what() << endl;
#endif

        // In the error scenario, the edgeList is not properly
        // deleted. Cannot add to the destructor of EdgeList
        // (as it should) because
        // "graph.addEdges(edgeList.getEdges());" below
        // takes over edgeList ownership in the success case.
        edgeList.clearList();

        throw ex;
    }

#endif // ENABLE_EDGE_NODING_VALIDATOR }

    GEOS_CHECK_FOR_INTERRUPTS();

    graph.addEdges(edgeList.getEdges());

    GEOS_CHECK_FOR_INTERRUPTS();

    // this can throw TopologyException *
    computeLabelling();

    //Debug.printWatch();
    labelIncompleteNodes();
    //Debug.printWatch();
    //nodeMap.print(System.out);

    GEOS_CHECK_FOR_INTERRUPTS();

    /*
     * The ordering of building the result Geometries is important.
     * Areas must be built before lines, which must be built
     * before points.
     * This is so that lines which are covered by areas are not
     * included explicitly, and similarly for points.
     */
    findResultAreaEdges(opCode);
    cancelDuplicateResultEdges();

    GEOS_CHECK_FOR_INTERRUPTS();

    PolygonBuilder polyBuilder(geomFact);

    // might throw a TopologyException *
    polyBuilder.add(&graph);

    vector<Geometry*>* gv = polyBuilder.getPolygons();
    size_t gvsize = gv->size();
    resultPolyList = new vector<Polygon*>(gvsize);
    for(size_t i = 0; i < gvsize; ++i) {
        Polygon* p = dynamic_cast<Polygon*>((*gv)[i]);
        (*resultPolyList)[i] = p;
    }
    delete gv;

    LineBuilder lineBuilder(this, geomFact, &ptLocator);
    resultLineList = lineBuilder.build(opCode);

    PointBuilder pointBuilder(this, geomFact, &ptLocator);
    resultPointList = pointBuilder.build(opCode);

    // gather the results from all calculations into a single
    // Geometry for the result set
    resultGeom = computeGeometry(resultPointList, resultLineList, resultPolyList, opCode);

    checkObviouslyWrongResult(opCode);


#if USE_ELEVATION_MATRIX
    elevationMatrix->elevate(resultGeom);
#endif // USE_ELEVATION_MATRIX

}

/*protected*/
void
OverlayOp::insertUniqueEdge(Edge* e)
{
    //Debug.println(e);
#if GEOS_DEBUG
    cerr << "OverlayOp::insertUniqueEdge(" << e->print() << ")" << endl;
#endif

    //<FIX> MD 8 Oct 03  speed up identical edge lookup
    // fast lookup
    Edge* existingEdge = edgeList.findEqualEdge(e);

    // If an identical edge already exists, simply update its label
    if(existingEdge) {

#if GEOS_DEBUG
        cerr << "  found identical edge, should merge Z" << endl;
#endif

        Label& existingLabel = existingEdge->getLabel();

        Label labelToMerge = e->getLabel();

        // check if new edge is in reverse direction to existing edge
        // if so, must flip the label before merging it
        if(!existingEdge->isPointwiseEqual(e)) {
            labelToMerge.flip();
        }
        Depth& depth = existingEdge->getDepth();

        // if this is the first duplicate found for this edge,
        // initialize the depths
        if(depth.isNull()) {
            depth.add(existingLabel);
        }

        depth.add(labelToMerge);

        existingLabel.merge(labelToMerge);

        //Debug.print("inserted edge: "); Debug.println(e);
        //Debug.print("existing edge: "); Debug.println(existingEdge);
        dupEdges.push_back(e);
    }
    else {
        // no matching existing edge was found
#if GEOS_DEBUG
        cerr << "  no matching existing edge" << endl;
#endif
        // add this new edge to the list of edges in this graph
        //e.setName(name+edges.size());
        //e.getDepth().add(e.getLabel());
        edgeList.add(e);
    }
}

/*private*/
void
OverlayOp::computeLabelsFromDepths()
{
    for(auto& e : edgeList.getEdges()) {
        Label& lbl = e->getLabel();
        Depth& depth = e->getDepth();

        /*
         * Only check edges for which there were duplicates,
         * since these are the only ones which might
         * be the result of dimensional collapses.
         */
        if(depth.isNull()) {
            continue;
        }

        depth.normalize();
        for(int i = 0; i < 2; i++) {
            if(!lbl.isNull(i) && lbl.isArea() && !depth.isNull(i)) {
                /*
                 * if the depths are equal, this edge is the result of
                 * the dimensional collapse of two or more edges.
                 * It has the same location on both sides of the edge,
                 * so it has collapsed to a line.
                 */
                if(depth.getDelta(i) == 0) {
                    lbl.toLine(i);
                }
                else {
                    /*
                     * This edge may be the result of a dimensional collapse,
                     * but it still has different locations on both sides.  The
                     * label of the edge must be updated to reflect the resultant
                     * side locations indicated by the depth values.
                     */
                    assert(!depth.isNull(i, Position::LEFT)); // depth of LEFT side has not been initialized
                    lbl.setLocation(i, Position::LEFT, depth.getLocation(i, Position::LEFT));
                    assert(!depth.isNull(i, Position::RIGHT)); // depth of RIGHT side has not been initialized
                    lbl.setLocation(i, Position::RIGHT, depth.getLocation(i, Position::RIGHT));
                }
            }
        }
    }
}

struct PointCoveredByAny: public geom::CoordinateFilter {
    const vector<const Geometry*>& geoms;
    PointLocator locator;
    PointCoveredByAny(const vector<const Geometry*>& nGeoms)
        : geoms(nGeoms)
    {}

    void
    filter_ro(const Coordinate* coord) override
    {
        for(size_t i = 0, n = geoms.size(); i < n; ++i) {
            Location loc = locator.locate(*coord, geoms[i]);
            if(loc == Location::INTERIOR ||
                    loc == Location::BOUNDARY) {
                return;
            }
        }
        throw util::TopologyException("Obviously wrong result: "
                                      "A point on first geom boundary isn't covered "
                                      "by either result or second geom");
    }

private:
    // Declare type as noncopyable
    PointCoveredByAny(const PointCoveredByAny& other) = delete;
    PointCoveredByAny& operator=(const PointCoveredByAny& rhs) = delete;
};

void
OverlayOp::checkObviouslyWrongResult(OverlayOp::OpCode opCode)
{
    using std::cerr;
    using std::endl;

    assert(resultGeom);

#ifdef ENABLE_OTHER_OVERLAY_RESULT_VALIDATORS

    if(opCode == opINTERSECTION
            && arg[0]->getGeometry()->getDimension() == Dimension::A
            && arg[1]->getGeometry()->getDimension() == Dimension::A) {
        // Area of result must be less or equal area of smaller geom
        double area0 = arg[0]->getGeometry()->getArea();
        double area1 = arg[1]->getGeometry()->getArea();
        double minarea = min(area0, area1);
        double resultArea = resultGeom->getArea();

        if(resultArea > minarea) {
            throw util::TopologyException("Obviously wrong result: "
                                          "area of intersection "
                                          "result is bigger then minimum area between "
                                          "input geometries");
        }
    }

    else if(opCode == opDIFFERENCE
            && arg[0]->getGeometry()->getDimension() == Dimension::A
            && arg[1]->getGeometry()->getDimension() == Dimension::A) {
        // Area of result must be less or equal area of first geom
        double area0 = arg[0]->getGeometry()->getArea();
        double resultArea = resultGeom->getArea();

        if(resultArea > area0) {
            throw util::TopologyException("Obviously wrong result: "
                                          "area of difference "
                                          "result is bigger then area of first "
                                          "input geometry");
        }

        // less obvious check:
        // each vertex in first geom must be either covered by
        // result or second geom
        vector<const Geometry*> testGeoms;
        testGeoms.reserve(2);
        testGeoms.push_back(resultGeom);
        testGeoms.push_back(arg[1]->getGeometry());
        PointCoveredByAny tester(testGeoms);
        arg[0]->getGeometry()->apply_ro(&tester);
    }

    // Add your tests here

#else
    ::geos::ignore_unused_variable_warning(opCode);
#endif

#ifdef ENABLE_OVERLAY_RESULT_VALIDATOR
    // This only work for FLOATING precision
    if(resultPrecisionModel->isFloating()) {
        validate::OverlayResultValidator validator(*(arg[0]->getGeometry()),
                *(arg[1]->getGeometry()), *(resultGeom));
        bool isvalid = validator.isValid(opCode);
        if(! isvalid) {
#ifdef GEOS_DEBUG_VALIDATION
            cout << "OverlayResultValidator considered result INVALID" << endl;
#endif
            throw util::TopologyException(
                "Obviously wrong result: "
                "OverlayResultValidator didn't like "
                "the result: \n"
                "Invalid point: " +
                validator.getInvalidLocation().toString() +
                string("\nInvalid result: ") +
                resultGeom->toString());
        }
#ifdef GEOS_DEBUG_VALIDATION
        else {
            cout << "OverlayResultValidator considered result valid" << endl;
        }
#endif
    }
#ifdef GEOS_DEBUG_VALIDATION
    else {
        cout << "Did not run OverlayResultValidator as the precision model is not floating" << endl;
    }
#endif // ndef GEOS_DEBUG
#endif
}

} // namespace geos.operation.overlay
} // namespace geos.operation
} // namespace geos

